1. Field of the invention
The present invention relates to a downhole swivel joint assembly and to a method of using said swivel joint assembly and furthermore to a wellbore clean-up assembly comprising said downhole swivel joint assembly and to a method of using said clean-up assembly.
2. The prior art
It is known in the gas and oil drilling industries to use a swivel joint assembly in wellbore clean-up operations to allow an uphole section of drill string to be rotated whilst a connected downhole section of string remains stationary. In these prior art swivel joint assemblies, a shear ring/pin arrangement is provided for allowing release of the assembly from an unactivated configuration, in which the uphole and downhole sections are locked to one another, and an activated configuration, in which the components are permitted to rotate relative to one another. It will be understood however that, once the shear ring/pin has sheared so as to allow movement from the unactivated configuration to the activated configuration, the assembly cannot then be retained in the unactivated configuration with the same effectiveness. The prior art swivel joint assemblies are arranged so that, when they are tripped uphole after having been activated, they will return to the unactivated configuration. However, with the primary means for retaining the assembly in the unactivated configuration no longer in place, subsequent movement of the assembly in a downhole direction and in a high wellbore drag environment (as encountered in high angle and horizontal wellbores) will frequently result in the assembly undesirably moving to the activated configuration. This is due to wellbore drag resisting movement of the assembly in a similar way to a landing profile provided within a wellbore for the purpose of activating an assembly. With the assembly arranged in an activated configuration as it is being run downhole, it is not possible for the downhole section to be rotated and this can be a disadvantage in certain operations. Furthermore, the prior art swivel joint assemblies used in clean-up operations incorporate vent apertures which are opened in moving from the unactivated configuration to the activated configuration and then allow cleaning fluid to be ejected from the interior of the assembly onto the wellbore casing to be cleaned. However, the vent apertures cannot be opened independently of the uncoupling of the uphole and downhole sections of the swivel joint assembly. This can be restrictive in certain clean-up operations. Prior art swivel joint assemblies also have poor rotational speed and load bearing performance which the applicant believes is due to their use of thrust plates as a bearing mechanism.
It is an object of the present invention to provide an improved downhole swivel joint assembly and wellbore clean-up assembly.
It is also an object of the present invention to provide an improved method of cleaning a wellbore.